What means "blob" in ipfs.draft3.pdf?

Theris file object named “blob” on page 7 and 8,
I thought it was a typo, but it meet again here { "data": "some data here", // blobs have no links } and in next paragraph. Explain please what kind of object is it ?

A “blob” in this context is just a chunk of bytes, where the system is unaware of any internal structure. For example, a .png file is a blob. JSON can be a blob too if you don’t parse it out into a dag. You can also think of blobs as leaf nodes in the dag.